Imagine an organisation that knows what you like, what you don’t like, where you live, where you shop, and how much you spend. Imagine all these data held on a central database, accessible from thousands of locations around the country by unknown operators at their whim.

It sounds scary written down; even ominous. Yet this is exactly the information loyalty cards such as the Tesco Clubcard or Nectar card provides.

Are most people bothered by this? Quite the contrary. Most people seem happy to allow these data to be collected about …